In general, a mobile communication system was developed to provide voice services while guaranteeing activity of users. However, the mobile communication systems have extended their fields to the data providing services beyond the voice communication providing service and have now developed to such a level at which they can provide high speed data service. However, since resources are lacking and users demand higher speed services in the mobile communication system providing a current service, a more advanced mobile communication system is needed.
To meet these demands, standardization of Long Term Evolution (LTE) is being progressed by the 3rd Generation Partnership Project (3GPP) as one of the next generation mobile communication systems that are being developed. LTE is a technology of implementing high speed packet based communication with a transmission rate of up to about 100 Mbps. To this end, several methods are being discussed, including a method of reducing the number of nodes located on a communication channel by simplifying a network architecture, a method of making wireless protocols closely access a wireless channel to the maximum, and the like.
Meanwhile, in recent years, a UE has appeared to which both a communication function (hereinafter, referred to as 3GPP or LTE) of receiving a communication service through the existing service provider network and a function of accessing the WLAN are provided. The WLAN can be used for providing a provider network service while being connected to the service provider network or for providing an Internet service while being directly connected to an Internet network.